Rear bumper for an automobile



FIG. 1 is a front perspective view of a rear bumper for an automobile showing our new design;

FIG. 2 is a left-side view thereof;

FIG. 3 is a right-side view thereof;

FIG. 4 is a front view thereof; and,

FIG. 5 is a top view thereof.

The rear surface has not been shown and is not intended to be part of the claimed design. Any small portions of the rear surface that can be seen in the front perspective view are not part of the claimed design. 

The ornamental design for a rear bumper for an automobile, as shown and described. 